[0z5a]

Refs gh-161387.

_decimal.current_context() returned whatever the internal decimal_context ContextVar held, without checking PyDecContext_Check. Callers immediately cast the value to PyDecContextObject *, so setting the variable to a non-context (for example 1) segfaults on the next decimal operation.

Raise TypeError from current_context() when the stored value is not a context. CURRENT_CONTEXT already propagates NULL, so callers fail cleanly.

Tests: new CContextAPItests.test_current_context_var_wrong_type. Built current main (5aa2f705) with the C _decimal extension (libmpdec 2.5.1): the reproducer exits with SIGSEGV (rc=139) before the change and raises TypeError after. The new test and the full test_decimal suite (751 tests, 9 skipped) pass.

[0z5a]

Addressed in c10e2e7: the error now reports the received type (expected a Context instance, got int), and the test now finds the matching context vars, saves reset tokens, restores them via a helper, and only then asserts the TypeError.

[sobolevn]

Please, assert that after the exception is handled: context var must not be cleared. Its value must not change